Update 3/9/2015: I just updated this article to include a previously undocumented dependency, that both Lync and Outlook must be on the same version for this to work.

Here is an interesting scenario that reveals a lot about how Lync Online operates. Let’s assume that two companies plan to merge and they want to have Instant Messaging and Presence between the two companies.

One company, ABC Corp has Lync 2010 on-premises and the other company, XYZ Corp has Lync Online. Both companies have enabled federation.

Both companies would like a shared Global Address List (GAL), and they plan to use Microsoft FIM 2010 R2 GALSync, so that user objects in one forest are copied as contact objects in the other forest.

The last requirement is to have the ability to search for the Lync external contacts within the Lync client itself.

Tips:

By default GALSync does not replicate the SIP address attribute “msRTCSIP-PrimaryUserAddress”, so GALSync must be modified to include this attribute. Additionally, mailnickname and targetaddress is required for Azure Active Directory Synchronization to export the object to Office 365 so that it is accessible for the Lync Online users. For a list of which attributes are synced by DirSync, click (here).
When populating the msRTCSIP-PrimaryUserAddress field, make sure to pre-pend with the sip: in front of the address.
When the targetaddress field is populated, be sure to pre-pend with SMTP: in front of the email address. For more info, see this article.
mailNickname can be populated with the contents of sAMAccountName
sAMAccountName, displayname, and CN cannot be blank.

Brajesh Panda wrote a fantastic walkthrough for modifying GALSync to include the msRTCSIP-PrimaryUserAddress attribute. However, it does not mention Lync Online. I wanted to write this blog article to add clarity on how external contacts can appear in Lync Online in a very limited scenario:

1. Outlook must be configured for cached Exchange Mode (this is the default configuration for Exchange Online).

[Update 3/9/2015] 2. Outlook and Lync must be on the same version (ex: Lync 2013 and Outlook 2013). Crossing versions is not supported and will not work (ex: Lync 2013 and Outlook 2010).

Additionally, external contact search is not available for Lync Mobile, OWA or Lync for Mac. The rest of this article explains why.

Unified Contact Store (UCS)

Lync Online is a “wave 15” product, and therefore is written to take advantage of the new Unified Contact Store (UCS). This is significant because according to my test results, search lookups in Lync Online appear to only query the UCS, and the UCS does not include information from the Global Address List (GAL) according to this MSFT article.

Therefore, when Lync Online is formatting its EWS query, it appears to exclude external contacts and only include licensed Lync Online users. This applies to the following Lync Online clients that exclusively rely on EWS for lookups: Lync Mobile, Lync for Mac OSX, and Lync presence when integrated into OWA. The only Lync client that can search and find external contacts is the Lync client for Windows when installed on a computer with Outlook configured for cached mode, with a local copy of the Offline Address Book. This is because Lync is designed to supplement the EWS query with an additional MAPI query to Outlook when Outlook is configured for cached exchange mode.

Note: When troubleshooting, remember that the OAB does not download immediately after a fresh Outlook profile is created, so it can take some time before external contacts will appear (see below for more information on how to check for this).

Goodbye Lync Address Book

Lync Online does not download a Lync address book. This is the opposite behavior of the Lync on-premises Server. Instead, Lync Online clients that want to lookup a contact will perform a web services query in two parts. The first query depends on whether an EWS connection is available and established (note: this requires the Exchange autodiscover record to be correctly configured to point to Exchange Online). Then, Lync Online is also configured to query the local Outlook via a MAPI connection to the local Outlook profile installed on the same local workstation that Lync is installed on, and it passes the query to Exchange on behalf of Lync. It is worth noting that when Outlook is configured for Online mode, then the MAPI connection that Lync makes to Outlook then uses the same EWS query against the UCS instead of the GAL (and therefore does not return external contacts). Again, cached mode is required.

Lync Online can only query external contacts in the GAL when the local Outlook client is configured for cached mode. Additionally, the SIP address of the user performing the search should match their email address otherwise the EWS and MAPI connection will fail and the user may receive authentication prompts. Also keep in mind that any updates to external contacts in the GAL will not be visible in Lync until the next time the Offline Address Book (OAB) is downloaded by the Outlook client (approximately once per day). This can take as long as 48 hours in a worst case scenario, consider the behavior by design:

Exchange Online mailbox server generates a new OAB at 5:00 AM (once every 24 hours)
Exchange distributes the OAB to the CAS servers (Default distribution schedule: 480 minutes)
Outlook downloads the OAB (Default update schedule: 24 hours)

This means that in the worst possible scenario, an update to the Address Book won’t become available to the user until 48 hours after the change.

Example:

Monday at 09:00 – Outlook client downloads the OAB

Monday at 14:00 – A new mailbox is created

Tuesday at 05:00 – Exchange OAB Generation runs

Tuesday at 09:00 – Outlook client checks for new OAB

Tuesday at 11:00 – OABVirtualdirectory is updated

Wednesday at 09:00 – Outlook client downloads the new updates.

So yes, all of the stars must align in order for the Lync client to search for external contacts. But it does work!

Here is evidence of an external contact replicating and being searchable with Lync Online:

The local contact “Jed Hill” was created in on-premises Active Directory:

Here is the DirSync export showing this object was copied to Lync Online

Next, download the Offline Address Book. You can check to see if the offline address book was downloaded by checking the timestamps in this directory:
C:\Users\(UserName)\appdata\local\microsoft\Outlook\Offline Address Books\ (long number)
Go into the subfolder and you should see several .OAB files:

And here is a screen shot of me searching for the external contact by first name and it returning Jed Hill. Ignore the fact that it says presence unknown, because I picked a fake SIP address for testing.

You can force the Outlook client to update more frequently by the methods described in this blog article here:

http://www.howto-outlook.com/howto/oabupdate.htm

Search Limitations

The limitations have already been mentioned, but to recap, external contacts will not be searchable within Lync Mobile, Lync for Mac. Also, keep in mind that when Outlook is in Online Mode, then the regular Lync client for Windows won’t be able to search for external contacts. The work-around for all these scenarios is for each user to type in the full SIP address to communicate with each external contact that is not already pinned or saved as a favorite in their Lync contact list.

IM/Presence Limitations

Here is a screen shot that shows Exchange Online OWA integration with Lync Online does not show presence or IM button for the External Contact. Whereas the full Outlook client will show the IM button when responding to an email with an external contact with a SIP address.

Lync Online users can pin up to 250 contacts to their Lync Contacts list.
Lync Online users each have a total of 200 concurrent presence subscriptions. Once that limit is reached, users can still send and receive instant messages and add users to a Contacts list, but they cannot see any additional presence information and will see a “Maximum Followers Reached” message when attempting to view a user’s presence

For more information on Lync Online features and limitations, see the Lync Online Services Descriptions here:
http://technet.microsoft.com/en-us/library/lync-online-instant-messaging-presence-and-contacts.aspx

References:

http://www.amintavakoli.com/2013/01/how-does-integration-between-outlook.html

http://tech.rundtomrundt.com/2011/10/forcing-lync-client-to-use-mapi.html

http://www.lync.geek.nz/2014/04/lync-2013-exchange-integration.html

http://msexchangeguru.com/2013/05/10/lync-and-exchange/